The subject invention relates generally to high energy explosives and more specifically to extrusion cast explosive compositions.
High energy explosives, such as those used in nuclear weapons, have been formulated to have high detonation pressures and high detonation energies. In order to attain these energy levels and to exhibit these properties, such compositions would require a high volume percent of the crystalline explosive which can be achieved only by compression molding or melt casting. Melt-cast explosives generally include crystalline explosives such as octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, commonly known as octogen or HMX; hexahydro-1,3,5-trinitro-1,3,5-triazene, commonly known as hexogen or RDX. As a result, these compositions are not thermally stable beyond about 80.degree. C. Compression moldable compositions normally use very high volume percent of solids in a plastic matrix. In more recent times, cast-cure compositions with relative thermal stability, have been designed and formulated but, have low or inadequate explosive energy for many applications. An extrusion cast explosive (ECX) is an improvement of the cast-cure type of explosive and is an explosive composition which can be extruded or transferred by fluid or plastic flow into a mold of any desired shape or size and then cured in place to yield the finished explosive in a relatively rigid and stable form.
U.S. Pat. No. 4,289,551 issued to Perrault et al., discloses a pour-cast-cure high energy explosive utilizing either HMX or RDX, a hydroxy-terminated polybutadiene based binder, a diisocyanate as the curing agent, a chemically compatible surfactant and, optionally, a plasticizer.
U.S. Pat. No. 4,050,968 issued to Goldhagen et al., describes a cast-cure explosive using HMX, RDX or perchlorate salts, a readily curable, elastomeric, hydroxyethyl acrylate copolymer as a binder, a diluent or plasticizer, an isocyanate as the cross-linking agent and, optionally, fuels or stabilizers or antioxidants or polymerization catalysts or explosive desensitizers. The polymer is prepared by a free radical initiated solution polymerization or emulsion polymerization.
U.S. Pat. No. 4,043,850 issued to Hoffmann et al., teaches slurry-cast propellants using HMX crystals. The HMX crystals are coated with a solution consisting of benzene and poly-aryl phenylisocyanate in methyl chloride, water and triethylamine, to provide a polyurethane coating on the crystals. A secondary coating may be applied by reacting the residual isocyanates with ethanol.
U.S. Pat. No. 3,778,319 to Benzinger et al., describes a high energy plastic-bonded explosive of 95% HMX, and 2.5% DNPA/F which is a eutectic mixture of the formal and acetal of 2,2-dinitropropanol as the plasticizer. The plasticizer is a thermoplastic, polyurethane elastomer, manufactured by B. F. Goodrich Company and sold under the trade name of Estane, which is prepared from long chain diols and toluene diisocyanate.
U.S. Pat. No. 3,480,490 issued to Finger et al., discloses a high explosive composition for extrusion-casting consisting of HMX or RDX dispersed in liquids of the gem-dinitro aliphatic class, such as FEFO and including therein gelling agents or active polymeric ingredients for curing.
Most of these formulations, however, do not meet the necessary, high performance criteria of high energy/explosive density, uniform consistency, greater homogeneity, low sensitivity to mechanical stimulants, low toxicity, stability over long storage times, and simplicity of handling.